Senior Mechanical Engineer Russ Landry presented his research on Commercial condensing boilers at the 2016 Natural Gas Conservation Convention.

1. COMMERCIAL CONDENSING
BOILER OPTIMIZATION
Russ Landry, PE, LEED®AP
Senior Mechanical Engineer
This project was supported in part by a grant from the Minnesota
Department of Commerce, Division of Energy Resources through the
Conservation Applied Research and Development (CARD) program.

2. Pg. 2
How Condensing Boilers
Outperform Conventional Boilers
• Conventional Boilers
• All “steam” goes out the vent
• Safety factor to prevent condensation limits efficiency
• Condensing Boilers
• A portion of the steam is used for heating
• No safety factor

3. Condensing Efficiency “Boost”
• 1 pound of captured steam heats 50 pounds of water
3
=
20°F
Rise

4. Condensing Boiler Efficiency Improvement
80% 85% 90% 95% 100%
Condensing--Your Building
Condensing--Ideal
Condensing--Minimum
Conventional Boiler
Conventional
Condensing
?????
If condensate drain dry

5. 3 Rules for “Energy Value” of
Condensing Boiler System
1) Low Return Water Temperature!
2) Low Return Water Temperature!
3) Low Return Water Temperature!

6. Condensing Boiler Efficiency Dependence
on Operating Conditions

7. Boiler System Temperatures in Real
Buildings & Impact on Efficiency
-20°F
0°F
20°F
40°F
60°F
80°F
100°F
120°F
140°F
160°F
180°F
Boiler Entering Water Temperature Outdoor Temperature
Condensation
Threshold

8. Flow Impact on Boiler Efficiency Via
Entering Water Temperature
Typical Flow

9. Flow Impact on Boiler Efficiency Via
Entering Water Temperature
Typical Flow
Low Flow

10. Reduced Flow Improves Boiler Efficiency...
Via Entering Water Temperature
Typical Flow
Low Flow

11. Pg. 12
Traditional Burner Tuning: Excess Air Up
Chimney & Reduced Condensing
86%
88%
90%
92%
94%
96%
98%
80°F 90°F 100°F 110°F 120°F 130°F 140°F
BoilerEfficiency
Boiler Return Water Temperature
20% Excess Air (3.8% O2)

12. Pg. 13
Traditional Burner Tuning: Excess Air Up
Chimney & Reduced Condensing
86%
88%
90%
92%
94%
96%
98%
80°F 90°F 100°F 110°F 120°F 130°F 140°F
BoilerEfficiency
Boiler Return Water Temperature
20% Excess Air (3.8% O2)
30% Excess Air (5.3% O2)

13. Pg. 14
Traditional Burner Tuning: Excess Air Up
Chimney & Reduced Condensing
86%
88%
90%
92%
94%
96%
98%
80°F 90°F 100°F 110°F 120°F 130°F 140°F
BoilerEfficiency
Boiler Return Water Temperature
20% Excess Air (3.8% O2)
30% Excess Air (5.3% O2)
40% Excess Air (6.5% O2)

14. Project Overview: Condensing Boiler
Optimization
• Preliminary Market Study & Site Selection
• Monitoring & Analysis of 12 Buildings
• 4 Education
• 4 Multifamily
• 4 Government/Office
• Industry Survey
• Dissemination

15. Minnesota’s Condensing Boiler Market
Study Findings
• Market Dominance of Condensing Boilers
• Condensing boilers have become the default choice
• Used in all building types that have space heating boilers
• Efficiency Concerns Noted
• Manufacturer’s reps acknowledge often suboptimal situations
• Part-load efficiency improvements may be significantly
overstated in some cases

16. Project Overview: Condensing Boiler
Optimization
• Preliminary Market Study & Site Selection
• Monitoring & Analysis of 12 Buildings
• 4 Education
• 4 Multifamily
• 4 Government/Office
• Industry Survey
• Dissemination

17. Estimated Annual Efficiency Based on
Monitored Conditions
80% 85% 90% 95% 100%
ED1
ED2
ED3
ED4
GO1
GO2
GO3
MF1
MF2
MF3
MF4
Hybrid Operating Efficiency
Condensing Operating Efficiency
Condensing Rated Efficiency

18. Potential Efficiency with Proposed
Features
80% 85% 90% 95% 100%
ED1
ED2
ED3
ED4
GO1
GO2
GO3
MF1
MF2
MF3
MF4
Plant Operating Efficinecy
Potential with Measures
Condensing Rated Efficiency

19. Potential Savings by Design Feature
Measure Type # of Sites
Average of
Sites with
Measure
Average
Across
All Sites
Reset Control 10 1.54% 1.40%
Burner Tune Up 10 0.80% 0.72%
Staging Control 8 1.15% 0.83%
Variable Speed
Pumping
10 0.48% 0.44%
Piping Change 5 2.06% 0.94%
Total 11 3.97%

20. Cost-Effective Retrofits After
Installation Completed
Site
Outdoor
Reset
Burner
Tune-Up
Staging
Control
Variable
Speed
Pumping Piping
Package
Cost
Package
Savings
(Therms)
Payback
(Years)
ED1 X X X O X $8,800 4,437 2.8
ED2 X X O $1,600 789 2.9
ED3 X X X O $3,100 2,822 1.6
ED4 X X X O $2,600 768 4.8
GO1 X X X $13,500 4,379 4.4
GO2 X X $2,750 5,248 0.7
GO3 X O O O $250 229 1.6
MF1 X X O O $3,400 1,217 4.0
MF2 O O O O NA NA
MF3 X X O O $620 376 2.4
MF4 X X X O $800 420 2.7
Sum 10 8 5 2 1 $37,420 20,686 2.6
X = Included; O = Excluded; Blank = No Opportunity

21. Survey: Most Commonly Witnessed
Issues Impacting Efficiency
Issue Percent
Turning off and on frequently (short cycling) 67%
Difficulties coordinating control between a BAS and
the boiler(s) 61%
Piping arrangements circulate water through an
idle, non-condensing boiler 44%
Boiler minimum temperature limited by the need to
heat service hot water 44%
Outdoor reset control does not lower temperature
as much as it could in mild weather 39%

22. Project Overview: Condensing Boiler
Optimization
• Preliminary Market Study & Site Selection
• Monitoring & Analysis of 12 Buildings
• 4 Education
• 4 Multifamily
• 4 Government/Office
• Industry Survey
• Dissemination

23. Survey Findings:
Primary Boiler Control System
On Board Controls
BAS Tie-In
Separate Dedicated Controls
0%
10%
20%
30%
40%
50%
Rarely
Sometimes
Often
Almost
Always

24. Survey: What Would be Most Worthwhile to
the Owner for Future Installations
Potential Program Element Percent
a. Piping Design Review 11%
b. Control Sequence Review 11%
c. Site-Specific Savings Estimate 6%
d. Bonus Rebate for Quality Design 11%
e. Bonus Rebates for Individual Design Features 6%
f. Commissioning of Installation and Controls 44%
g. New Training Options for Designers & Installers 11%

25. Survey: What Would be Most Worthwhile to
the Owner for Previous Installations
Potential Program Element Percent
a. Specialized Engineering Review 11%
b. Gas Rebate for Variable Speed Drive 6%
c. Rebates for Control Upgrades 6%
d. Rebates for Optimizing Control Settings 17%
e. Resources on Optimal Control & Operation 11%
f. Site-Specific Guide for Controls 6%
g. New Training Options for Operators 44%

26. Project Overview: Condensing Boiler
Optimization
• Preliminary Market Study & Site Selection
• Monitoring & Analysis of 12 Buildings
• 4 Education
• 4 Multifamily
• 4 Government/Office
• Industry Survey
• Dissemination

27. Dissemination of Project Findings
• Presentations:
• 2014 CenterPoint Energy Technology Conference
• 2015 AEE/ASHRAE Twin Cities Energy Expo
• 2016 Minnesota Blue Flame Gas Association’sNatural Gas
Conservation Conference [will be downloadable on Minnesota Blue
Flame Gas Association website]
• Detailed final report--available soon (pending review)
• Future webinar--utility program issues focus

28. In Conclusion…
• While less than simple rating values suggest, condensing boiler
savings is still large in nearly all buildings
• Maximizing savings depends on:
• Minimizing temperature settings (outdoor reset adjustment)
• Optimal boiler staging control programming
• Burner tuning of air-fuel ratio to lower limit
of recommended oxygen range
• Avoiding sub-optimal piping
• Possible utility program developments
• Support for specialized commissioning
• Support for new operator training options
• Rebates for optimization of control settings

29. Thank You
This project was supported in part by a grant from the Minnesota
Department of Commerce, Division of Energy Resources through
the Conservation Applied Research and Development (CARD)
program.
Russ Landry, PE, LEED®AP
rlandry@mncee.org